Foaming back brush



FIG. 1 is a perspective view of an ornamental design for a foaming back brush;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof, the left side being a mirror image;

FIG. 4 is a rear view thereof;

FIG. 5 is a bottom plan view of FIG. 2; and,

FIG. 6 is a top plan view of FIG. 2. 

I claim the ornamental design for a foaming back brush, as shown and described. 